Surface Roughness Profile and Its Effect on Coating Adhesion and Corrosion Protection

Modern design, manufacturing and field testing specifications include surface profile and adhesion testing on the assumption that they are linked to long term corrosion prevention. There are a number of careful studies, dating back decades, that find no link between measurements of adhesion and (undercutting) corrosion performance, but other studies do, and the concept remains intuitively appealing and widely assumed. Finding connections between adhesion, corrosion and surface profile requires a detailed understanding of fracture mechanics, surface energy, viscoelasticity and even nano-science. Simple measures of surface roughness are not sufficient to correlate with the adhesive strength of coatings. In addition, common “pull-off” adhesion testing cannot characterize the forces between the coating and metal substrate that might prevent water etc. invading that interface. Modern science can dispel some contradictions, but does not yet give unequivocal guidance on the choice of polymer coating for the best corrosion protection in practical situations.